You too can have a dream body; in your movies - tech - 07 October 2010 - New Scientist

Expect to see thinner models at a cinema near you.

Although the results are realistic, extreme alterations slightly distort a film's background.
Which presumably presupposes that the alteration will be from fat to thin. Some male characters might want more muscles.

They did a good job in that film containing Vinni Jones, in which they piled muscles on him. Perhaps that was done frame by frame.